“Citizen Kane” is one of the greatest movies ever — witty, visually inventive, unforgettable and fun. But not until Ben Mankiewicz saw the film in college did he finally get what all the fuss was about.

Mankiewicz, now a host on Turner Classic Movies cable network, called home and told his dad, “Hey, this movie your father wrote is actually quite good.”

Citizen Kane” co-screenwriter Herman J. Mankiewicz, who died in 1953, wrote some of the best and most popular movies of all time. His son Frank skipped a career in film and became a top aide to Democratic Sens. Robert Kennedy and George McGovern during their presidential runs.

Frank’s son Ben Mankiewicz grew up in Washington in the 1970s and 1980s in what he called the “political wing” of his family. But on TCM for the past decade, he has found a niche bringing movies of his grandfather’s day to a modern audience.

On Sunday, Ben and Frank Mankiewicz are hosting a Father’s Day lineup on TCM that includes “Citizen Kane” (1941), which ranks first among the American Film Institute’s greatest films of all time. As a tribute to Frank Mankiewicz’s political career, TCM is also screening “All the King’s Men” (1949) with Broderick Crawford and “The Last Hurrah” (1958) with Spencer Tracy.

The wild card is “Smokey and the Bandit” (1977), essentially one long car chase between Burt Reynolds and an exasperated sheriff played by Jackie Gleason. Ben Mankiewicz, who is 45, chose it because it was the first film he remembers seeing with his father.

They banter as the day of films begins.

Frank: “Happy to be here.”

Ben, deadpan: “Thanks very much. I’d like to believe that.”

They discuss Herman Mankiewicz’s shared screenwriting credit with director Orson Welles on “Citizen Kane.” Mankiewicz and Welles won the Oscar for their story, but Frank Mankiewicz says, “It was not written at all by Orson Welles.” He recalls that Welles “begged” his father for co-authorship because Welles’s receiving his full salary for the movie depended on getting the writing credit in addition to directing, acting in and producing “Citizen Kane.”

Yet there are equally knowledgeable Welles supporters who say the director is unfairly maligned as a credit hog. The debate over who really wrote the movie is unlikely to be resolved soon.

‘Enormous treasure chest’

TCM’s role in spurring such discussions — and in simply showing thousands of films hard to find anywhere else, even with Netflix — is a reason that many viewers have an almost fanatical devotion to the network. Director and writer Peter Bogdanovich and Rock Hall of Famer Tom Petty refuse to stay in hotels that do not offer TCM.

“The good movies from the past, it’s an enormous treasure chest of entertainment and charm and quality and humor and drama and everything else,” said Bogdanovich, whose movie credits include “The Last Picture Show” (1971). “It’s a tremendous loss in people’s lives if they don’t know what preceded them.”

He added that Ben Mankiewicz’s affable style brings value to the network because “he doesn’t make it seem like medicine.”

Mankiewicz calls himself a “knowledgeable fan” trying to communicate his admiration with an ironic style that casual viewers might appreciate.

As host, he pokes gentle fun at some of the stars and plots. The 1958 best picture Oscar winner, “Gigi,” Mankiewicz mock-warned viewers in one of his introductions, was “not to be confused with ‘Gigli,’ the ‘Bennifer’ disaster that won’t get anywhere near the Oscars.”

At a live TCM event a few years ago, he cheekily introduced Eva Marie Saint, long married and a star of 1950s dramas “On the Waterfront” and “North by Northwest,” as a reckless tabloid personality, “the Lindsay Lohan of her day.” The audience laughed.

Film scholar Jeanine Basinger said she was startled when she first saw Mankiewicz on TCM. He was young and goateed, a former broadcast journalist who brought an irreverence that was in sharp relief to Robert Osborne, the urbane, silver-haired film historian who served as host since the network launched in 1994. Osborne, 81, remains the principal host.

“I am a huge fan of Robert Osborne,” Basinger said. “He’s my age group, he grew up with films I grew up with. I felt so utterly in tune with him. Along comes this young guy — a little more edge, willing to make a little fun of the movies. Osborne is saying, ‘We know and we love these films, let’s look at these films together.’ Mankiewicz is saying, ‘We don’t know what this is, let’s take a look at this together.’ ”

Of hosting, Mankiewicz said, “You have to be able to maintain your reverence without losing your sense of fun. They aren’t all ‘Casablancas.’ It isn’t all ‘The Third Man’ ” — two undisputed great films.

“And laughing along at a confining studio system, at ridiculous gender and race roles [in some of the films] doesn’t mean you can’t enjoy these movies,” he said. “But you don’t always have to speak in hallowed terms. For me, it’s just speaking about it honestly and, because I do revere them, I think people will get that.”

The road to TCM

Herman Mankiewicz and his younger brother Joseph L. Mankiewicz, who died in 1993, were major creative forces in Hollywood. Individually, they wrote screenplays for some of the leading actors of the day, including Gary Cooper (“Pride of the Yankees”), Bette Davis (“All About Eve”) and Elizabeth Taylor (“Cleopatra”).

Herman’s son, Frank, now 89, avoided a movie career after seeing how it embittered his father, an alcoholic who he said despised Hollywood but thought the money was too good to refuse. Frank became press secretary to Robert Kennedy and campaign director of McGovern’s 1972 presidential bid.

The political work was consuming, and he was often away from home. Ben Mankiewicz said he rebelled at age 5 by telling people he wanted President Richard Nixon to beat McGovern in 1972. After Nixon won by a landslide, Frank Mankiewicz went on to run National Public Radio before moving into public relations.

Ben Mankiewicz was co-captain of the basketball team at the private Georgetown Day School and graduated from Tufts University in Massachusetts and Columbia University’s journalism school. He hoped to follow the broadcast reporting career of his older brother, Josh, now a correspondent for “Dateline NBC.”

After shuffling among various jobs in TV news, most auspiciously in Miami, Mankiewicz got his first taste of criticism in 2008 when he and Ben Lyons briefly replaced Roger Ebert and Richard Roeper as hosts on “At the Movies.”

Mankiewicz said it was “really difficult” to receive stinging feedback, “but it’s hard to be a movie critic and be angry about getting a negative review. I get the hypocrisy in complaining about that.”

By that time, he was well into his career as a weekend daytime host at Turner Classic Movies. The slot was important to the network, because executives saw viewers sampling the channel during those hours. Sean Cameron, who is now vice president of production at the channel, said Mankiewicz was hired to “look at films more from a film fan’s appreciative point of view.”

TCM, which is commercial-free, does not divulge its viewership numbers. But Cameron said bringing in Mankiewicz was not rooted in any concern about luring younger watchers. “Our fan base skews a lot younger than people would think,” he said. “Sixty percent of our audience is under 54. That’s a pretty large fan base who will grow with us, so we don’t need to skew young to draw them. They’re already there with us.”

Mankiewicz’s job has gradually expanded to include Thursday nights and Sunday late nights in addition to appearances at the annual TCM movie festival in Hollywood. His home base is Santa Monica, Calif., where he lives with his girlfriend, Lee Russo, and their infant daughter, Josie.

Mankiewicz said he is compensated well as a TCM host — a point that would please Herman, who could be scathing in his assessment of Hollywood. He imagines his grandfather saying, “You’re being paid not for writing but for just talking about movies? Well done, young man. Well done.”